Dili Village Telco Part 9 – The Network builds

In the 4 weeks since I left Dili Lemi and his team have been busy building out the pilot Dili Village Telco. Here is a map of the installed nodes (click for a larger image):

The lines between nodes may not be accurate – the mesh network will form links on an ad-hoc basis.

Significant effort has been required to set up each link (days of effort, several return visits). The quality metric we look for is a “ping -s 1400″ packet loss of less than 10% and clear quality speech on the phone calls.

Some patterns are emerging. All of the non-trivial links (Eiros, both University sites) have required a Nanostation 2. These links would not function with just a Mesh Potato. Omni-directional antennas struggle in the interference-rich environment of Dili. I have found a similar problem on my test mesh here in suburban Adelaide – several 100 metre links links with omni-directional antennas suffer poor packet loss.

This is an unfortunate result – mesh networks depend on omnidirectional antennas, but omnidirectional antennas suffer from interference. This is an expensive and unwieldy Catch 22 – on nodes at the end of long distances links we are requiring both a Nanostation 2 and a Mesh Potato:

This is very expensive (due to the cost of the Nanostation 2) and awkward to set up as a directional antenna require alignment. The network is more fragile as the link quality is sensitive to small shifts in the physical positioning of the mast (mast arrangements tend to be less robust in the developing world). It also requires more specialised training and knowledge to set up.

I am hoping that as the network density builds and the nodes get closer together (e.g. 50m or less), the need for directional antennas and hence Nanostations will reduce. We might be looking at a backbone based on directional antennas, with many mesh nodes hanging off each backbone link in a star topology.

Lemi reports a clear win for the Village Telco concept between the two University sites, “But at the University they are very happy because now they don’t need to use mobile to call each other.” This is a key, but often overlooked “killer app” for the Village Telco – local calls over a few 100m. In many parts of the world there are no land lines or even PBX systems and the only way to call another office is a 50 cents/minute GSM call. Note that no server, billing system or PSTN gateway is required for this killer application – just a network of mesh potatoes.

I think the lack of external connectivity is what makes this killer app so hard to understand for 1st world people – we intuitively associate VOIP with long distance and a PSTN gateway of some kind is always part of the picture. We have forgotten how magical a simple local call is.

To their credit the Fongtil guys now have 7 sites (10 nodes) operational:

1. Blind Union (MP)
2. University Caicoli Next to Blind Union (MP+NS2)
3. University Liceu (MP+NS2)
4. Ase Training Center (MP)
5. FTM (eyes of human right) (MP)
6. FONGTIL (2 MP+2NS2+LENOVO SERVER)
7. EIROS (MP+NS2) next to Tiger Fuel

This demonstrates another important principle of the Village Telco – some smart local guys with minimal training can set up an operational mesh telephone network. Where we still need work is the “ease of setup” meme – setting up reliable links has been difficult, expensive and time consuming in Dili.

Another important metric is up-time – how reliable is the network? Can people rely on it to make phone calls? As the network builds we will gather experience and data on up-time. We will also get some data on scalability – this will be the first time a 100 node Village Telco network has been attempted.

This completes WP3000 of the Project Plan – April workshop and 10 node Pilot network. Next step (WP4000) is to supply 90 more Mesh Potatoes to build the 100 node network over the next few months. Atcom have been kindly working very hard at assembling a special batch of MPs for this project, which should be ready for deployment in June.

Links

Dili Village Telco Project Wiki
Dili Village Telco Part 1
Dili Village Telco Part 2
Dili Village Telco Part 3
Dili Village Telco Part 4
Dili Village Telco Part 5
Dili Village Telco Part 6
Dili Village Telco Part 7
Dili Village Telco Part 8

1 comment to Dili Village Telco Part 9 – The Network builds

  • Jay Christopherson

    A tool that I use is a custom asterisk extension that plays a constant tone. With this I can hear if there are problems with drops, compression, bandwidth, etc. I have it do the ‘thank you, good by’ so I know that the connection was not just dropped. This has helped tremendously for diagnosing issues we had with wifi phones on a different system.

    exten => s,1,Answer
    exten => s,n,PlayTones(1004)
    exten => s,n,Wait(1800)
    exten => s,n,StopPlayTones
    exten => s,n,Playback(thank-you-for-calling)
    exten => s,n,Playback(vm-goodbye)
    exten => s,n,Hangup

Leave a Reply

 

 

 

You can use these HTML tags

<a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>